Big ideas: Climate change

Why should the human race care about climate change? Because its impacts could pose an unprecedented challenge to human society.

The basic cause of climate change is an increase in the atmospheric concentration of greenhouse gases, of which carbon dioxide is the most prominent. In the pre-industrial era, the concentration of carbon dioxide in the atmosphere was about 280 parts per million (ppm). By 2000 it was 368 ppm. Figures from the first few years of this millennium indicate a continuing increase, and projections for the end of this century indicate a range of 540 to 970 ppm.

The higher the concentration of greenhouse gases in the atmosphere, the greater the warming of the Earth. The range of temperature increases projected for the end of this century lies between 1.4 and 5.8 °C above 1990 levels. Total warming during the 20th century is estimated to have been 0.6 °C.

The ...

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